Circular knitting machine having a device for severing yarn



Dec. 10, 1963 a. BlLLl ETAL 3,113,443

CIRCULAR KNITTING momma HAVING A DEVICE FOR SEVERING YARN Filed Feb. 15, 1961 M/VE/V T085: (Frans a 8/1 United States Patent CIRCULAR KNHTTING MACHINE HAVING A DEVECE FOR SEVERIWG YARN Giorgio Billi, Vials Torricelli 23, Florence, and Viniclo Luchi, Via Lavilla 179, Galceti-Prato, Florence, ltaly Filed Feb. 15, 1961, Ser. No. 89,502 Claims priority, application Italy Feb. 15, 195i) 4 lliainrs. (til. 66-145) This invention relates to a device for severing yarn in a circular knitting machine. in particular the device is intended for severing the yarn extending from a yarn guide which has just been raised out of its yarn feed position. The device is designed to sever the yarn closely adjacent the point at which it leaves the fabric being formed, so as to eliminate further cutting after the formation of the tubular fabric. In this way the relatively high percentage of waste occurring at this stage due to the sensitiveness of the fabric and the possibility of a thread being broken or a stitch being pulled, so producing a defect in the fabric, may be substantially reduced.

According to the present invention there is provided in a circular knitting machine a device for severing yarn adjacent the path of movement of the needles. The device comprises a pair of cutters extending adjacent the path of movement of the needles and located to re ceive yarn extending between a yarn guide and the last needle which has taken the yarn. The cutters are relatively movable to edect a scissoring or shearing action in which the opening movement of the cutters is very fast in relation to the closing movement thereof.

The invention will be better understood from the following description and the accompanying drawing which set forth one embodiment of the invention. in the drawing:

FIG. 1 is a diametral section taken on a plane passing through the needle cylinder axis of a circular knitting machine having a yarn severing device;

FIG. 2 is a plan view of the machine of 1;

FIG. 3 shows a detail of PEG. 2;

FZGS. 4 and 5 show cutters forming part of the yarn severing device.

As is shown diagrammatically in the accompanying drawing, the circular knitting machine has needles 1 mounted in a needle cylinder 2 which is coaxial with a stationary cover 3, disposed above the needle cylinder. A rotary plate 4 supporting the welt hooks 5 is driven by means of a shaft (not shown) passing through the hub 4a of the plate.

The severing device comprises a stationary arcuate cutter 3 having a concave cutting edge be directed towards the axis of rotation of the plate 4. Cooperating with the cutter 8 is a second cutter 11 which is also arcuate and is pivoted to the cutter 8 on a pin ll passing through the bore 9 in the cutter 8 (see PEG. 5). The second cutter 11 has a convex cutting edge lla which cooperates in a scissors action with the cutting edge 8a. The cutter 11 is urged by a helical spring 12 surrounding the pin it in a direction angularly away from the stationary cutter 8. The cutter ll is engaged by a tappet rod 14 which is slidable longitudinally in a passage substantially radial with respect to the axis of rotation of plate 4. The passage is formed in the stationary cover 3. The

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rod 14- is urged axially by the spring 12. acting through the cutter 11, against a cam 15 having a plurality of peaks or teeth. The cam is fixed coaxially to the hub in of the plate 4 and accordingly is rotated therewith. The profile of the cam 11 is shaped similarly to a ratchet wheel with each tooth having a generally radially extending edge and an inclined convexly curved edge. The profile of each tooth of the cam is so shaped that upon rotation of the cam 15, the tappet rod 1 is pushed outwards gradually by the curved edge of each tooth but returns with a much faster movement along the radial edge of the tooth. In this way, the angle between cutting edges 11:: and 8a of the cutter Ill and the cutter 8 is closed relatively slowly but is opened rapidly by action of the spring 12 when the peak of each tenth of the cam has passed the tappet rod M.

This operation effects a scissoring or shearing action between the cutting edges 53a and 11a of the cutters 8 and 11. For this operation, cam ill rotates counterclockwise as viewed in FIGS. 2 and 3.

Yarn which extends between a yarn-guide, raised out of the feed position, and the last needle which has taken the yarn, is introduced, by the movement of the needle cylinder, between the cutting edges 8a and 11a of the two cutters 8 and T1, and is thus severed by the scissoring action of the cutters. Conventional means (not shown) must be provided for holding the severed yarn. As the cutting edges extend along the path of movement of the needles, and as the closing movement of the cutters is relatively slow whilst the opening movement is very fast there is practically no interruption in the severing action since the cutter ll begins to move angularly towards the cutter 8 immediately after opening of the cutters and before the yarn has travelled the distance along the path of movement of the needles between the points at which the yarn is severed when the cutters are almost fully open and fully closed respectively.

The frequency of severing movement and the speed of the severing movement are determined respectively by the number of peaks on the cam and the inclination of each edge of the cam profile.

The drawing illustrates only one embodiment of the invention, given by way of example only and this may be considerably modified without departing from the scope of the invention as defined by the claims appended hereto.

Thus, for example both the cutters 8 and ll may be made movable or the cutter 8 may be movable and the cutter 11 be stationary.

Whilst the members 8 and 11 are referred to herein as cutters having cutting edges, no distinction is intended to be drawn between cutters and shears, or between scissoring and shearing action.

What we claim is:

1. In a circular knitting machine having a cylinder rotatable on its axis and carrying a plurality of needles in a circular path, yarn guides located adjacent the cylinder to feed yarns to the needles and a plate carrying welt hooks disposed over the cylinder, said plate being rotatable on an axis aligned with the axis of rotation of the cylinder, a yarn severing device comprising a pair of cutters disposed adjacent the cylinder and extending close to said path, said cutters having intersecting cutting edges for engaging therebetween yarn to be severed extending from the yarn guides to the needles, said cutters being relatively movable to effect opening and closing movements of t e cutting edges, spring means biasing the cutters to an open position, a cam carried by said plate and rotatable on the axis of rotation of the piate, said cam having a plurality of equally spaced teeth all around its periphery, each of said teeth having a first edge extending generally radially to the axis of rotation of the plate and having another edge extending angularly to said first edge, and a cam follower movably supported between said cam and one of the cutters and tracking on the edges of the cam to open the cutting edges relatively rapidly and to close the cutting edges relatively slowly a multiplicity of times during each revolution of the cam.

2. A device according to claim 1, wherein one of said cutting edges is concave and the other of said cutting edges is convex.

3. A device according to claim 1, further comprising a stationary plate disposed between said earn and cutters, said stationary plate having a passage therein, said cam follower being a rod disposed in said passage.

4. A device according to claim 3, wherein said spring 163118 and cutters are carried by said stationary plate.

References Cited in the file of this patent UNITED STATES PATENTS 1,677,477 Herbert July 17, 1928 2,090,228 Porter et al. Apr. 11, 1935 2,961,858 Wiesinger Nov. 29, 1960 

1. IN A CIRCULAR KNITTING MACHINE HAVING A CYLINDER ROTATABLE ON ITS AXIS AND CARRYING A PLURALITY OF NEEDLES IN A CIRCULAR PATH, YARN GUIDES LOCATED ADJACENT THE CYLINDER TO FEED YARNS TO THE NEEDLES AND A PLATE CARRYING WELT HOOKS DISPOSED OVER THE CYLINDER, SAID PLATE BEING ROTATABLE ON AN AXIS ALIGNED WITH THE AXIS OF ROTATION OF THE CYLINDER, A YARN SEVERING DEVICE COMPRISING A PAIR OF CUTTERS DISPOSED ADJACENT THE CYLINDER AND EXTENDING CLOSE TO SAID PATH, SAID CUTTERS HAVING INTERSECTING CUTTING EDGES FOR ENGAGING THEREBETWEEN YARN TO BE SEVERED EXTENDING FROM THE YARN GUIDES TO THE NEEDLES, SAID CUTTERS BEING RELATIVELY MOVABLE TO EFFECT OPENING AND CLOSING MOVEMENTS OF THE CUTTING EDGES, SPRING MEANS BIASING THE CUTTERS TO AN OPEN POSITION, A CAM CARRIED BY SAID PLATE AND ROTATABLE ON THE AXIS OF ROTATION OF THE PLATE, SAID CAM HAVING A PLURALITY OF EQUALLY SPACED TEETH ALL AROUND ITS PERIPHERY, EACH OF SAID TEETH HAVING A FIRST EDGE EXTENDING GENERALLY RADIALLY TO THE AXIS OF ROTATION OF THE PLATE AND HAVING ANOTHER EDGE EXTENDING ANGULARLY TO SAID FIRST EDGE, AND A CAM FOLLOWER MOVABLY SUPPORTED BETWEEN SAID CAM AND ONE OF THE CUTTERS AND TRACKING ON THE EDGES OF THE CAM TO OPEN THE CUTTING EDGES RELATIVELY RAPIDLY AND TO CLOSE THE CUTTING EDGES RELATIVELY SLOWLY A MULTIPLICITY OF TIMES DURING EACH REVOLUTION OF THE CAM. 